sql_union.cc:

  Merge fix

sql/sql_union.cc

@@ -31,9 +31,10 @@ int mysql_union(THD *thd, LEX *lex,select_result *result)
   ORDER *order;
   List<Item> item_list;
   TABLE *table;
-  int describe=(lex->select_lex.options & SELECT_DESCRIBE) ? 1 : 0;
-  int res, add_rows=0;
-  bool found_rows_for_union= lex->select_lex.options & OPTION_FOUND_ROWS;
+  int res;
+  ulonglong add_rows= 0;
+  ulong found_rows_for_union= lex->select_lex.options & OPTION_FOUND_ROWS;
+  ulong describe= lex->select_lex.options & SELECT_DESCRIBE;
   TABLE_LIST result_table_list;
   TABLE_LIST *first_table=(TABLE_LIST *)lex->select_lex.table_list.first;
   TMP_TABLE_PARAM tmp_table_param;
@@ -135,19 +136,29 @@ int mysql_union(THD *thd, LEX *lex,select_result *result)
   union_result->tmp_table_param=&tmp_table_param;
   for (sl= &lex->select_lex; sl; sl=sl->next)
   {
-    unsigned int rows;
+    ha_rows records_at_start;    
     lex->select=sl;
-    thd->offset_limit=sl->offset_limit;
+    /* Don't use offset for the last union if there is no braces */
+    thd->offset_limit= sl != lex_sl ? sl->offset_limit : 0;
     thd->select_limit=sl->select_limit+sl->offset_limit;
     if (thd->select_limit < sl->select_limit)
       thd->select_limit= HA_POS_ERROR;		// no limit
+    /*
+      When using braces, SQL_CALC_FOUND_ROWS affects the whole query.
+      We don't calculate found_rows() per union part
+    */
     if (thd->select_limit == HA_POS_ERROR || sl->braces)
       sl->options&= ~OPTION_FOUND_ROWS;
-    else if (found_rows_for_union)
+    else 
     {
-      rows= thd->select_limit;
-      sl->options|= OPTION_FOUND_ROWS;
+      /*
+ 	We are doing an union without braces.  In this case
+ 	SQL_CALC_FOUND_ROWS should be done on all sub parts
+      */
+      sl->options|= found_rows_for_union;
     }
+ 
+    records_at_start= table->file->records;
 
     res=mysql_select(thd, (describe && sl->linkage==NOT_A_SELECT) ?
 		     first_table :  (TABLE_LIST*) sl->table_list.first,
@@ -159,12 +170,23 @@ int mysql_union(THD *thd, LEX *lex,select_result *result)
 		     sl->having,
 		     (ORDER*) NULL,
 		     sl->options | thd->options | SELECT_NO_UNLOCK |
-		     ((describe) ? SELECT_DESCRIBE : 0),
+		     describe,
 		     union_result);
-    if (found_rows_for_union  && !sl->braces && sl->options & OPTION_FOUND_ROWS)
-      add_rows+= (thd->limit_found_rows > rows) ?  thd->limit_found_rows - rows : 0;
     if (res)
       goto exit;
+    /* Needed for the following test and for records_at_start in next loop */
+    table->file->info(HA_STATUS_VARIABLE);
+    if (found_rows_for_union & sl->options)
+    {
+      /*
+ 	This is a union without braces. Remember the number of rows that could
+ 	also have been part of the result set.
+ 	We get this from the difference of between total number of possible
+ 	rows and actual rows added to the temporary table.
+      */
+      add_rows+= (ulonglong) (thd->limit_found_rows - (table->file->records -
+ 						       records_at_start));
+    }
   }
   if (union_result->flush())
   {
@@ -217,12 +239,8 @@ int mysql_union(THD *thd, LEX *lex,select_result *result)
 		       item_list, NULL, (describe) ? 0 : order,
 		       (ORDER*) NULL, NULL, (ORDER*) NULL,
 		       thd->options, result);
-      if (found_rows_for_union && !res)
-      {
-	thd->limit_found_rows= table->file->records;
-	if (!last_sl->braces)
-	  thd->limit_found_rows+= add_rows;
-      }
+      if (!res)
+ 	thd->limit_found_rows = (ulonglong)table->file->records + add_rows;
     }
   }